Is the financing volume for our construction project realistic?

That is a good point, in addition to the risk of job loss there are other risks, including accidents, illness, or death. None of these can be ruled out and there can be no guarantees for many decades. Professionally, I have a good outlook, my partner has not yet taken the step to become a manager and will probably be able to take a step up in salary in a few years, at the latest when the children are in school or secondary school. In the end, I think one has to soberly acknowledge that if one becomes unemployed and the other requires care, we will have to sell the house and reorient ourselves.

I would also have liked to have already saved 100,000 euros more in equity, but unfortunately time cannot be turned back. If I had not been deterred by the stock market crash in 2003, but had invested even small amounts in a stock savings plan or saved elsewhere, it would of course be nicer from today’s perspective. However, we have both been all the more consistent and determined in recent years because priorities have clearly shifted in favor of family and home. That is why I have no problem paying the installment consistently over the years because I know exactly what a nice home means for my family.

There will be no horses, at least no own ones. It still needs to be clarified whether the two stable spaces can be rented out to other people. We already had a nearly 25 m³ pool, and the running costs were not extreme. I could imagine that with a hot tub, the costs mainly come from electricity. The pool circulation pump ran three times daily for two hours each during the season, and the chlorine consumption was surprisingly low. We currently live in a rented house >200m² and basically have all the furniture. Of course, the children will eventually need a bigger bed, desk, etc., but those are ongoing things from ongoing income. The kitchen is so far just a rough estimate; we still have appointments at the kitchen store. ;) However, I do believe that we are reasonably well-positioned here and the kitchen will not cost 50,000 euros.

You have used the most commonly used word in connection with the stock market: HÄTTE ;). I like it, it's somehow honest. Otherwise, I think it's very good when someone with a fairly modest income in relation to the overall project ventures into the discussion here. From experience, there are always between 10 and 20% added to the initially planned costs; you will therefore probably end up at around 1.2 million in the end. Considering the quite low equity share at that point, you will have to take out a bit more loan, but who doesn't do that nowadays? After some searching, it will somehow work out... just be brave!

How do you see the topic of inflation? The loan amount and the purchase price are measured in today's euros, the installment remains the same over 25 years (depending on the interest rate fixation and interest rate development, of course). Salaries, rent, and everything else will experience inflation, as the ECB targets 2% as the ideal value from their perspective. Doesn't inflation work in favor of the buyer then, and shouldn't one assume a certain probability that the net income in 20 years will be 1,000, 2,000, or 3,000 euros higher than today, while the installment is still 3,000 euros per month?

How do you see the topic of inflation? The loan amount and the purchase price are measured in today's euros, the rate remains the same over 25 years (depending on the interest rate lock and interest rate development, of course). Salaries, rent, and everything else will have inflation, the ECB targets 2% as the ideal value from their point of view. Doesn't inflation then work in favor of the buyer, and shouldn't one assume a certain probability that the net income in 20 years will also be 1,000, 2,000, or 3,000 euros higher than today, while the rate is still 3,000 euros per month?

Of course it is like that. No one just factors it in. With an assumed 1.5%/year, you can calculate what the debt is still worth in about 20 years.

Is the whole thing in the outdoor area?
Is the only condition really just a mini-stable, whose use then doesn't matter?
If outdoor area with the condition of agricultural use, be aware that even if everything gets approved, the value of the house will not come close to matching the investment.
What are you going to do with 1500m² of lawn?
I see ongoing costs for garden maintenance, as everything suggests no big DIYer is planned here.
Otherwise, of course, a solid thing considering the income.
You really must never be on sick leave for too long, otherwise the house will be gone and debts remain, see above.

No, it is on the outskirts in a rural area. There are definitely no restrictions such as agricultural use and it is not a mixed area with commercial use either. The lawn is very large, my current idea for lawn care is a robot or possibly a used ride-on mower. I have no problem mowing the lawn on weekends. We might also plant a few trees, but I wanted to look into that more closely once, for example, a building application has been submitted and I have some waiting time that I can use for such things. We will also take our trampoline and the sandbox with us. The grandparents want to donate a play tower made of wood with a slide and swing, which will reduce the lawn area a bit more.